328 
Part III. — Tenth Annual Report 
the distribution of immature flat fishes agree with those made on board 
the * Garland.' The author discusses the question of the protection of 
immature fish, and inclines to the view that certain fish should be pro- 
tected until they have reached a size above the minimum size at which 
maturity is attained. 
In the second of these are a number of papers dealing with marine 
biology, physics, and sea fisheries. Mr Calderwood, in his report, reviews 
the work of the Association, and refers to the investigations being carried 
on by Mr Holt at Grimsby, in connection with the North Sea Fisheries, 
the objects of which are (1) to prepare a history of the North Sea trawling 
grounds and their present condition, with their condition twenty or thirty 
years ago ; (2) to continue, verify, and extend observations as to the 
average sizes at which the various food-fishes become sexually mature ; (3) 
to collect statistics as to the quantity of immature fish captured annually ; 
(4) to make experiments with beam trawl-nets, with meshes of different 
size, to ascertain the relation between size of mesh and the size of the fish 
captured. Mr Holt furnishes a paper with a brief account of the method 
of his investigation, and some of the results obtained — giving limits for 
dividing large and small fish, comprising 22 species, among them the 
following: — Turbot, 17 inches; brill, 15; sole, 12; lemon-sole, 10; 
plaice, 17 ; halibut, 23 ; witch, 12; megrim (Arnoglossus), 12; sand-dab, 
6; long rough dab, 6; flounder, 7; cod, 20; haddock, 10; whiting, 8; 
coal-fish, 20; hake, 24; tusk, 16 ; gurnard, 9 ; cat-fish, 20.* Tables are 
given of a number of fish examined in January, February, and March. 
There is a paper by Mr Hughes on the continuation of the experiments 
on artificial bait ; there has been, up to the present, little or no success, 
the great difficulty being to discover a suitable medium for the retention 
of the organic extracts. 
Mr J. T. Cunningham gives an important paper ' On the Rate of 
' Growth of some Sea-Fishes, and the Age and Size at which they begin 
4 to Breed/ treating of the cod, flounder, common ,dab, sole, mackerel, 
herring, sprat, pilchard, anchovy, and shads. This research has been 
carried on partly by observations on fish of different sizes taken from the 
sea, in relation to their spawning time, and partly on specimens reared in 
tanks, the results and views of other observers being also discussed. No 
new light is thrown upon the rate of growth of the cod ; the earliest 
period at which sexual maturity is reached is uncertain. The measure- 
ments of flounders reared in the tanks are given ; the largest specimen 
known to be two years of age was 26*7 cm. long, or 10*5 inches, and the 
smallest only 7*2 cm. or 2*8 inches. Cunningham reasonably conjectures 
that this difference is due to artificial conditions, although it may possibly 
sometimes occur in nature. None of the flounders attained sexual maturity 
during the first year, and only 19 per cent in the second year; and the 
inference is that the majority breed when three years old. Of the speci- 
mens which became mature, 1 3 were males, and 4 were females ; but the 
observations extend only up to the end of March. The smallest ripe 
male was 6*4 inches and the largest 9 - 2 inches; the smallest ripe female 
was 8*4 inches and the largest 10*5. Cunningham infers that in 
order to exclude all immature individuals, a limit of size must be taken 
which is above the minimum size of mature females. It appears to me 
that too much stress may be laid upon results so obtained ; although it 
must be said the investigation of the rate of growth is as difficult as it is 
important, and in the absence of tidal ponds, such as Dannevig possessed, 
there is scarcely any other mode possible. If the fish is marked and 
returned to the sea, it is injured, and the natural rate of growth cannot 
* Compare Table V. at page 238 of the present Report. 
